WORKSHEETSCOUNT

Returns the number of sheets
For instructions on how to add a function to a workbook refer to the page under Inserting Functions

'bIncludeChartSheets - Whether to include chart sheets in the total.

Public Function WORKSHEETSCOUNT(Optional ByVal bIncludeChartSheets As Boolean = True) As Integer 

   If bIncludeChartSheets = True Then 
      WORKSHEETSCOUNT = Application.ActiveWorkbook.Sheets.Count 
   Else 
      WORKSHEETSCOUNT = Application.ActiveWorkbook.Worksheets.Count 
   End If 

End Function 

You can use the built-in worksheet function SHEETS() in Excel 2013 to return the number of sheets in the active workbook.

Migration

In Power Utility Pack this function is called SHEETCOUNT